MONTREAL — The Bruins had a welcome traveler on their charter flight after their 2-1 loss to the Montreal Canadiens Thursday night at the Bell Centre.

Johnny Boychuk, wheeled off the ice on a stretcher at 4:28 of the first period, was cleared to fly home. Boychuk injured his back when a Max Pacioretty hit from behind sent the defenseman into the end boards in the Montreal zone.

“To see how much pain he was in there — I think his back seized up on him or something like that — he thought he was going to be all right, then he wasn’t,” Jarome Iginla said. “It’s a scary sight, for sure, because he’s a very tough guy. If there’s any way he can get up and get off at that point, you know he would. So, it’s very tough to see.”

Boychuk was in immediate pain after the hit. He was on his hands and knees when trainer Don DelNegro arrived at his side. Boychuk appeared to have trouble catching his breath. DelNegro then waved for assistance.

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Several Montreal trainers hurried onto the ice. They called for a stretcher. Medical personnel carefully moved Boychuk onto his side. They then positioned Boychuk onto a board. With help from Zdeno Chara and Milan Lucic, the trainers lifted Boychuk onto a stretcher. Boychuk was taken by ambulance to Montreal General Hospital.

It is unknown how much time Boychuk will miss. The Bruins host the Penguins Saturday. The following night in Toronto, the Bruins start a four-game Canadian road swing that concludes in Vancouver Dec. 14.

“It was an injury serious enough to bring him to the hospital,” coach Claude Julien said. “Definitely, I think it will be a little while before he’s good to go.”

Boychuk’s flight home did not blunt the sting of the second period. The Bruins were up, 1-0, after 20 minutes. They winged 10 shots on Carey Price. One of them, a Gregory Campbell one-touch of Lucic’s backhand saucer, slipped past the Montreal goalie.

The Bruins were in good position to tuck it to the Canadiens. Montreal had gone to a shootout the night before in New Jersey. The Canadiens were playing their third game in four nights. The Bruins were coming off four rest days.

Instead, the Bruins tucked their tails in the second. They put only seven pucks on Price. At the other end, the fast-moving Canadiens, reaching back to their Flying Frenchmen days, poured 18 shots on Tuukka Rask. The Boston goalie wilted on one and couldn’t do much to stop another.

“Our second period was atrocious and embarrassing,” Julien said. “That cost us the game. If we would have played the middle period like we played the first and third, we’d be standing here with a win right now.”

The Bruins thrive on puck possession. They retrieve pucks rapidly from the defensive zone. The defensemen shuttle them up to their forwards. The attackers fly into the offensive zone to initiate their cycle.

None of that happened in Thursday’s second. The Canadiens claimed the puck as their own. They turned the Bruins into spectators. The Canadiens ripped off 30 second-period shots. Eighteen landed on goal. The Bruins blocked eight shots. The Canadiens missed with six others. The Bruins recorded only nine shot attempts. There is no way to win when the puck belongs to someone else.

The No. 2 line of Brad Marchand, Patrice Bergeron, and Loui Eriksson struggled the most. Through 40 minutes, the three combined for no shots and zero offensive presence.

“I don’t know,” Bergeron said when asked why the Bruins flickered in the second. “It wasn’t even close to the effort that we should bring. It cost us the game, obviously. I can’t really tell you why.”

A Rask misplay sparked Montreal’s rally. Rask was scrambling after Brian Gionta screamed a shot wide of the net. The Canadiens regained control of the puck to reset their attack. Tomas Plekanec settled it at the right circle.

Rask had time to square himself to Plekanec’s shot but left an opening over his left shoulder. Plekanec picked the hole at 9:16 to tie it at 1-1.

As culpable as Rask might have been for Plekanec’s goal, the goalie’s teammates did little to resist the Canadiens on the winning goal.

Brendan Gallagher started the rush by dangling around Iginla to gain a clean entry into the offensive zone. Gallagher handed the puck to Raphael Diaz, who curled into the slot and snapped a backhander on goal.

Rask booted out Diaz’s shot with his right pad but kicked the rebound into the high slot under the stick of a backchecking Campbell. Before Rask could recover, Pacioretty flipped a backhander into the net at 17:42.

The Bruins found their legs and their heads in the third. They hammered Price with 16 pucks. But Price turned them all back.

“We had a very strong first period and a very strong third period,” Iginla said. “But in the second, we got totally outplayed. We gave them a chance to find some life at home. We knew they’d played last night. We didn’t take advantage of it. You’ve got to play a full game. It got us in the second.”

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